As well as a "chunky" tread pattern, winter tyres are made from a softer compound of rubber which works better on tarmac at lower temperatures, below 7 degrees C, than normal tyres.
You either need an extra set of wheel rims or pay twice a year to have tyres re-fitted on your existing rims. Breakers seem to charge high for second-hand steel rims, it's often easier and chaeper to pick up s/h alloys with cosmetic damage.
Whether it's worth while fitting them depends how often you drive in country areas or go much above sea level.